There is substantial need for improving the effectiveness of medications for treating opioid use disorder (OUD), plus a considerable need to develop effective medications for cannabis use disorder (CUD). The novel overarching theme of this Center is to examine medications based on their ability to improve clinical sequelae common to both cannabinoid and opioid use disorders (i.e., abstinence-induced withdrawal and relapse), in part due to their shared common neurobiologic underpinnings. This Center consists of 4 Cores and 4 Projects with considerable synergy and interdependency. Unifying all of the Projects are the Administrative Core, the Research Core, the Pilot Project Core, and the Training and Education Core. In the first 2.5 years of this Center, Phase II clinical trials in Project 2 and Project 4 will test the combined cannabinoid/opioid strategy of combining nabilone and naltrexone for both CUD and OUD. Meanwhile, the human laboratory studies in Project 1 and Project 3 will evaluate medications (lorcaserin, cannabidiol, doxazosin, and zonisamide, potentially in combination with nabilone or buprenorphine or sustained-release naltrexone) using a priori decision algorithms to identify candidate medications to be tested in subsequent Phase II clinical trials in Projects 2 and 4. The Center has a clear organizational structure and will b conducted in a cost-efficient manner. The resources available to the research team, along with the institutional support, ensure the success in attaining the Aims of the Center. These include: 1) Use of efficient decision algorithms to test medications alone, and in combination, in the laboratory and move those that show a positive signal rapidly into the clinic; 2) Test these positive medications from the laboratory for efficacy in Phase II controlled trials; 3) Explore predictors of medication effects in the laboratory and clinic settings; 4) Train junior investigatos to become the next generation of leaders in substance abuse; and 5) Disseminate evidence-based research findings locally, nationally and internationally. This application builds on the strengths and achievements of our research team, while developing innovative advances in shared medications development for cannabinoids and opioids. Our innovative approach will ensure that our Center is synergistic, translational and at the cutting edge of medications development. In sum, this Center is strongly focused on using the most efficient approach to find potential pharmacologic agents to treat two disorders that are of great clinical concern, namely, cannabis and opioid use disorders.